Influences of long-duration NO exposure on CO2 adsorption on coals: insights into oxy-coal burning flue gas storage in coal reservoirs

Introducing oxy-coal burning flue gas into coal reservoirs has the advantages of mitigating emissions of CO2, NOx, and SO2, and producing in-situ coalbed methane (CBM). Given the characteristics of the geologic time scale for fluid sequestration, the long-duration NO exposure was conducted for various ranks of coal matrices to access the potential impacts of NO exposure on CO2 storage. Afterwards, the changes in critical physico-chemical properties and adsorbability of various ranks of coal matrices to CO2 because of long-duration NO exposure were revealed. Finally, the implications to implement oxy-coal burning flue gas sequestration in unmineable coal reservoirs with CBM production were indicated. The results demonstrate that the long-duration interaction with NO reduces the number of micro- and mesopores of various ranks of coals, especially those with diametres below 4.00 nm. Moreover, the long-duration NO exposure reduces the oxygen-containing functional groups while significantly increasing the amine/amide-N for all the coals. The aforementioned alterations in the surface chemistry property imply that the coal matrix is capable of chemically adsorbing NO, thereby achieving its stable storage in target coal reservoirs. Given the electron donor-acceptor interactions between amine/amide-N and CO2, the NO exposure can elevate the CO2 storage capability of various ranks of coals under typical reservoir temperature and pressure. In summary, introducing oxy-coal burning flue gas into coal reservoirs is capable of stably storing critical gaseous pollutants and simultaneously enhancing the CO2 storage potential of coal reservoirs, thereby updating the existing oxy-coal burning technology and CO2 sequestration in unmineable coal reservoirs with the enhanced CBM recovery technology. [GRAPHICS] .

Automated summary

Introducing oxy-coal burning flue gas into coal reservoirs can reduce CO2, NOx, and SO2 emissions and produce in-situ coalbed methane (CBM). Long-duration NO exposure experiments were conducted on various ranks of coal matrices to assess the potential impacts on CO2 storage. The results show that NO exposure can reduce the number of pores in the coal matrix and change its adsorbability to CO2, indicating the potential for stable storage of NO and enhanced CO2 storage capacity. Overall, introducing oxy-coal burning flue gas into coal reservoirs has the potential to improve the existing technology and enhance CO2 sequestration. [GRAPHICS].